6 Genomics of Marine Algae
199
projects exist for this group at the present time. However, a considerable amount
of information can be obtained by sequencing cDNA clones and individual genes
isolated from these genomes. ESTs data is currently available for several dinoflagellates, particularly species that produce toxic metabolites, such as Alexandrium
tamarense, A. catenella, Karenia brevis, Amphidinium carterae, Heterocapsa triquetra and Lingulodinium polyedrum (Genbank Sequence Database, Tanikawa et al.
2004, Hackett et al. 2005, Bachvaroff and Place 2008).
6.4.6 Macroalgal Genomics
In contrast to pelagic plankton communities, which contain primarily unicellular
algae, coastal ecosystems are often dominated by macroalgae of the brown, red and
green lineages. These three types of seaweed play key roles in coastal ecosystems,
not only as primary producers but also by providing habitats for a wide variety of
marine life. Seaweeds are also important from an evolutionary perspective. Brown,
red and green macroalgae represent diverse branches of the eukaryotic phylogenetic tree and each group has independently evolved complex multicellularity. This
independent evolution of complex multicellularity in the three seaweed groups is
particularly important as it has placed them in a very select club within the eukaryotes, shared with only three other lineages, the metazoans, land plants and fungi.
Marine macroalgae therefore represent an important resource for understanding how
complex developmental systems have evolved.
Seaweeds have also attracted interest for many other reasons. Fertilisation is
external in brown algae, involving fusion of gametes that have been released into the
surrounding seawater. This is a major advantage for the study of early developmental events compared, for example, to angiosperms where fertilisation occurs within
several layers of maternal tissue (Brownlee et al. 2001). Macroalgae also exhibit a
remarkably wide range of different life cycles, several of which are very complex,
making them ideal models to study how variant life cycles evolve and why they
are stable over evolutionary time (Coelho et al. 2007). Finally, seaweeds are also a
major source of food and industrial biomolecules such as alginates, agars and carrageenans. Seaweeds represent an important resource with a wide range of uses in
the food, cosmetic, and fertiliser industries and an estimated annual global value of
about 4.5 billion Euros (McHugh 2003). They are also attracting increasing attention as a novel source of active biomolecules. One example of this is IODUS 40, a
formulation derived from cell wall extracts of Laminaria digitata that stimulates the
natural defence responses of crop plants (Klarzynski et al. 2000).
The following sections will look at how genomic approaches are being used to
investigate the biology of macroalgae for each of the three phylogenetic groups.
6.4.6.1 Brown Macroalgae
The most evolved and morphologically complex members of the brown algae (or
Phaeophyceae) are found in the orders Laminariales and Fucales. These include the
199
projects exist for this group at the present time. However, a considerable amount
of information can be obtained by sequencing cDNA clones and individual genes
isolated from these genomes. ESTs data is currently available for several dinoflagellates, particularly species that produce toxic metabolites, such as Alexandrium
tamarense, A. catenella, Karenia brevis, Amphidinium carterae, Heterocapsa triquetra and Lingulodinium polyedrum (Genbank Sequence Database, Tanikawa et al.
2004, Hackett et al. 2005, Bachvaroff and Place 2008).
6.4.6 Macroalgal Genomics
In contrast to pelagic plankton communities, which contain primarily unicellular
algae, coastal ecosystems are often dominated by macroalgae of the brown, red and
green lineages. These three types of seaweed play key roles in coastal ecosystems,
not only as primary producers but also by providing habitats for a wide variety of
marine life. Seaweeds are also important from an evolutionary perspective. Brown,
red and green macroalgae represent diverse branches of the eukaryotic phylogenetic tree and each group has independently evolved complex multicellularity. This
independent evolution of complex multicellularity in the three seaweed groups is
particularly important as it has placed them in a very select club within the eukaryotes, shared with only three other lineages, the metazoans, land plants and fungi.
Marine macroalgae therefore represent an important resource for understanding how
complex developmental systems have evolved.
Seaweeds have also attracted interest for many other reasons. Fertilisation is
external in brown algae, involving fusion of gametes that have been released into the
surrounding seawater. This is a major advantage for the study of early developmental events compared, for example, to angiosperms where fertilisation occurs within
several layers of maternal tissue (Brownlee et al. 2001). Macroalgae also exhibit a
remarkably wide range of different life cycles, several of which are very complex,
making them ideal models to study how variant life cycles evolve and why they
are stable over evolutionary time (Coelho et al. 2007). Finally, seaweeds are also a
major source of food and industrial biomolecules such as alginates, agars and carrageenans. Seaweeds represent an important resource with a wide range of uses in
the food, cosmetic, and fertiliser industries and an estimated annual global value of
about 4.5 billion Euros (McHugh 2003). They are also attracting increasing attention as a novel source of active biomolecules. One example of this is IODUS 40, a
formulation derived from cell wall extracts of Laminaria digitata that stimulates the
natural defence responses of crop plants (Klarzynski et al. 2000).
The following sections will look at how genomic approaches are being used to
investigate the biology of macroalgae for each of the three phylogenetic groups.
6.4.6.1 Brown Macroalgae
The most evolved and morphologically complex members of the brown algae (or
Phaeophyceae) are found in the orders Laminariales and Fucales. These include the